1. Field of the Invention
The present invention relates to nozzles for air guns, and in particular to a venturi nozzle for an air gun which maximizes the volume of air discharged from the nozzle for a given volume of compressed air input thereto, and which minimizes the noise generated by the nozzle upon the passage of air therethrough.
2. Description of the Prior Art
In the manufacture and maintenance of various types of equipment, air guns are often employed to blow dust and other debris from the equipment. Air guns ordinarily operate with an input air pressure greater than 40 psi. However, as a result of one standard promulgated under the Occupational Safety and Health Act (OSHA), the maximum pressure generated at an air gun nozzle discharge tip when the nozzle is dead ended, such as by being placed against an operator's hand or a flat surface, must be less than 30 psi.
A known nozzle for alleviating the problem of dead ended pressure build up includes a restricted orifice within a central bore of the nozzle through which compressed air passes into a discharge end of the nozzle, and a plurality of circular apertures formed through the nozzle in the discharge end thereof. When the discharge end of the nozzle is dead ended, the compressed air therewithin passes through the circular apertures, or vent holes, to limit build up of pressure within the discharge end of the nozzle. As set forth in U.S Pat. No. 3,790,085, with this type of nozzle the vent holes are desirably located adjacent the restricted orifice so that when air is passed through the orifice an additional volume of air is aspirated into the main stream of air in the discharge end of the nozzle because of the venturi effect produced within the discharge end of the nozzle adjacent the orifice by the passage of the compressed air therethrough. In this manner, the vent holes not only allow trapped air to travel outward therethrough to reduce the pressure within the discharge end of the nozzle should the discharge end be blocked, but they also allow air to be drawn therethrough into the stream of air within the discharge end of the nozzle when the end of the nozzle is not blocked.
Moreover, in many instances, the compressors available to supply compressed air to guns are limited in capacity, resulting either in the inability to supply air continuously to any one air gun, or in the inability to simultaneously operate several air guns. While previous venturi nozzles have operated to increase the volume of air discharged from the exhaust hole of the nozzle for a given volume of compressed air input to the nozzle from the air gun, the increase obtained has not been of sufficient magnitude to permit satisfactory and efficient use of limited capacity compressors. It is, therefore, desirable that the design of the vented nozzle be such as to maximize the volume of air discharged therefrom for a given volume of compressed air input thereto.